Evolutions of defect filament and waveform in the defect-mediated dust acoustic wave turbulence
Jun-Yi Tsai1,2*, Lin I1
1Department of physics, National Central University, Taoyuan, Taiwan
2Molecular Science and Technology, Taiwan International Graduate Program, Academia Sinica, Taipei, Taiwan
* Presenter:Jun-Yi Tsai, email:zazartsai@gmail.com
With increasing driving, the transition from the ordered state to the weakly disordered state is a universal phenomenon in the nonlinear wave medium such as acoustic, plasma and optical system. Through modulation instability, the waveform in the weakly disordered state is spatiotemporally modulated, which causes the generation of defect filaments with null amplitudes and undefined phases. It leads to the name defect-mediated turbulence (DMT). In acoustic type waves, the defect filaments are located at the cores of the acoustic vortices, i.e. the singular core winded around by the helical waveform. Similar to the vortex filaments in the cores of vortices in hydrodynamic systems, those defect filaments can interact with one another. Those singular objects can be used to characterize the dynamics of the DMT states for nonlinear waves. However, their generic dynamical behaviors are still unexplored. In this work, this issue is experimentally addressed in a weakly disordered self-excited dust acoustic wave (DAW) in the dusty plasma system composed of micrometer sized particles negatively charged and suspended in a low pressure discharge, by monitoring the spatiotemporal waveform evolution in the 2+1d space-time space. It is found that defect filaments can aggregate in the form of clusters exhibiting a power law cluster size distribution. The local filament curvature in the xyt space is strongly correlated to the short range interaction, which in turn affects the local waveform evolution of DAW.

Keywords: dusty plasma, defect-mediated turbulence, defect filament, dust acoustic wave